Ringing circuit for use in portable telephone set

ABSTRACT

A portable telephone set having a ringing circuit for producing different ringing tones depending upon the use mode of the portable telephone set, a portable mode or a mobile mode. The ringing circuit comprises a mode detecting circuit for detecting the use mode, an internal loudspeaker housed in a housing of the portable telephone set for producing a first ringing signal when the portable telephone set is in the portable mode, an external loudspeaker connected externally of the housing for producing a second ringing signal when it is in the mobile mode and a ringing tone generator for generating a first and a second ringing tones for driving the respective loudspeakers producing first and second ringings. The first and second ringing tones have frequency spectra compatible with frequency characteristics of these loudspeakers to produce the respective ringings efficiently. The ringing signal generator may be a single ringing tone generating circuit producing two kinds of ringing tone or may be comprised of two different ringing tone generating circuits.

This is a divisional of Application No. 07/648,759 filed Jan. 31, 1991now U.S. Pat. No. 5,303,284.

BACKGROUND OF THE INVENTION

The present invention relates to a portable telephone set and, moreparticularly, to a portable telephone set having a ringing circuit andto be used in a portable mode and mobile mode.

There has been known a portable telephone set which has two use-modes,i.e., a portable mode in which the telephone set is used by a user whilebringing it with him and a mobile mode in which it is mounted on avehicle. In the portable mode, a compact and light-weight, built-inloudspeaker is used. In the mobile mode, a relatively large externalloudspeaker is used because the loudspeaker outputs not only a ringingtone but also a voice signal and thus the voice quality therefrom playsan important role.

In general, in the above-mentioned ringing circuit, the built-in, i.e.,internal loudspeaker is compact and has narrow frequency characteristicswhile the external loudspeaker has relatively wide frequencycharacteristics. In the conventional ringing circuit, however, a ringingsignal having a single frequency spectrum is used. Thus, when thefrequency characteristics of the internal and external loudspeakers aredifferent, there may be a problem that the energy of a ringing signalfor driving the loudspeaker cannot be used effectively. More definitely,when the ringing signal spectrum is broad and the internal loudspeakeris used, a portion of the frequency spectrum of the ringing signal whichis not used increases and the power consumption of a ringing signalgenerating circuit is undesirably increased. On the other hand, when theringing signal frequency spectrum is narrowed to adjust it to theinternal loudspeaker, it is impossible to supply enough power to theexternal loudspeaker, so that an effective ringing sound cannot begenerated.

Furthermore, the switching between the internal and externalloudspeakers is manually carried out. This manual switching is atroublesome operation for the user.

SUMMARY OF THE INVENTION

An object of the present invention is, therefore, to provide a ringingcircuit for use in a portable telephone set which circuit is capable ofproducing an effective ringing sound for either an internal or externalloudspeaker thereof to be used.

Another object of the present invention is to provide a ringing circuitfor use in a portable telephone set which circuit automatically switchesinternal and external loudspeakers based on the use conditions of theportable telephone set.

According to the present invention, there is provided a portabletelephone set having two use-modes, portable mode and mobile mode, andincludes a mode detecting circuit for detecting the use-modes. Upon acall from a base station, a ringing circuit of the portable telephoneset generates a ringing sound from an internal loudspeaker thereof whenthe portable mode is detected or from an external loudspeaker when themobile mode is detected. In the portable mode, the ringing circuitproduces a first ringing signal having a frequency spectrum adjusted tofrequency characteristics of the internal loudspeaker and, in the mobilemode, produces a second ringing signal having a frequency spectrumadjusted to frequency characteristics of the external loudspeaker. Theringing circuit may include two ringing signal generating circuits whichgenerate the first and second ringing signals, respectively. Further,the ringing circuit may include a single ringing signal generatingcircuit which generates the first or second ringing signal dependingupon the use-mode detected. When the external loudspeaker is connectedto the telephone set, an input terminal of the mode detecting circuit isgrounded simultaneously and this grounding signal can be used as thedetection signal of the mode detection circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other objects, features and advantages of thisinvention will become more apparent by reference to the followingdetailed description of the invention taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a schematic block diagram showing a portable telephone setaccording to an embodiment of the present invention;

FIG. 2 is a flowchart explaining the call reception operation of theFIG. 1 portable telephone set;

FIG. 3 is a schematic block diagram showing a specific construction ofthe speaker/microphone of the FIG. 1 embodiment;

FIG. 4 shows frequency characteristics of an internal loudspeaker and anexternal loudspeaker which are used in the FIG. 3 embodiment;

FIG. 5 is a schematic block diagram showing a ringing tone generator ofthe speaker/microphone portion shown in FIG. 3;

FIG. 6 is a schematic block diagram showing a mode detecting circuitused in the FIG. 3 embodiment;

FIG. 7 is a schematic block diagram showing another specificconstruction of speaker/microphone portion of the FIG. 1 embodiment; and

FIG. 8 is a schematic block diagram showing a ringing tone generator ofthe speaker/microphone portion shown in FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, a portable telephone set 10 can be carried by the user ormounted on a vehicle. The telephone set 10 has an antenna 1 picking up aradio frequency (RF) signal and radiating an RF signal. The antenna 1may be replaced by or switched to a vehicle-mounted antenna when thetelephone set 10 is mounted on the vehicle. The picked-up RF signal issupplied to a receiver portion 3 through an antenna duplexer 2. Thereceiver portion 3 demodulates the received RF signal to produce anaudio frequency (AF) signal which may include a voice signal and a datasignal. The voice signal is supplied to a speaker/microphone portion 5to be outputted from a speaker circuit 12 or a handset 14 therewithin.The handset 14 may include an earpiece receiver and a mouthpiecemicrophone. The data signal is supplied to both a call detector circuit7 and a control circuit 9.

The speaker/microphone portion 5 includes a microphone circuit 13 aswell as the speaker circuit 12 and the handset 14. The microphonecircuit 13 and speaker circuit 12 are used for the so-called hands-freetelephoning in which the user can make conversation through thesecircuits 12 and 13 without resorting to the handset 14. The hands-freetelephoning can be performed only when the telephone set 10 is mountedon a vehicle. In this case, the speaker circuit 12 is used forconversation and for generating an audible ringing tone. When thetelephone set 10 is used as a portable one, the handset 14 is used forconversation and the speaker circuit 12 is dedicated to generating anaudible ringing tone.

A voice signal is inputted through the microphone circuit 13 or thehandset 14 and supplied to a transmitter portion 4. The transmitterportion 4 is also supplied with a data signal from the control circuit 9and various signals from a signal generator 6. The transmitter portion 4transmits the supplied signals to a base station (not shown) of a mobilecommunications system through the duplexer 2 and the antenna 1. Thesignal generator 6 generates the various signals under the control ofcontrol circuit 9. The control circuit 9 also controls the receiver andtransmitter portions 3 and 4, especially to cause them to tune to adesired radio frequency channel in a well-known manner.

The call detector circuit 7 detects from the supplied data signal acalling signal addressed to the telephone set 10 and produces a calldetection signal. The call detection signal is led to both the controlcircuit 9 and speaker/microphone circuit 5. In response, thespeaker/microphone circuit 5 generates an audible ringing tone throughthe speaker circuit 12 to alert the user to a call.

The telephone set 10 further includes a mode detect circuit 8 whichdetects the use condition of the telephone set 10. More specifically, ifthe telephone set 10 is used as a portable set, the mode detect circuit8 produces a portable-mode signal. If the telephone set 10 is mounted ona vehicle, the mode detect circuit 8 produces a mobile-mode signal. Uponthe mobile-mode signal, the control circuit 9 may switch from theantenna 1 to the vehicle-mounted antenna.

In response to the portable-mode signal, the speaker circuit 12generates a first audible ringing tone whose frequency is suitable to aninternal speaker accommodated in the telephone set 10, which will bedescribed later. On the other hand, in response to the mobile-modesignal, the speaker circuit 12 generates a second audible ringing tonewhose frequency is suitable to an external speaker to be connected tothe telephone set 10, which will also be described later. Since thefrequencies of the ringing tones are so selected, it is possible toproduce an audible ringing tone at the maximum level with the minimumpower consumption.

In FIG. 2, the portable telephone set 10 waits at step S11 for a callcoming through a so-called paging channel which is one of controlchannels for broadcasting calling signals and various control signalsfrom a base station to portable or mobile telephone sets. If thetelephone set 10 receives a calling signal addressed thereto at step S12and detects it with the call detect circuit 7, the control circuit 9causes the signal generator 6 to generate a response signal. The controlcircuit 9 further causes the transmitter portion 4 to transmit at stepS13 the response signal to the base station. Thereafter, the controlcircuit 9 checks at step S14 if it receives a channel designate signalindicating a designated speech channel. If the control circuit 9 doesnot receive the channel designate signal within a predetermined periodof time, the operation returns to step S11. Otherwise, the controlcircuit 9 causes the receiver and transmitter portions 3, 4 to tune tothe designated speech channel at step S15.

Step S15 is followed by step S16 at which the use condition of telephoneset 10 is checked using the mode detect circuit 8. If the set 10 is usedas a portable set, the speaker circuit 12 generates a portable-moderinging tone whose frequency is suitable to the internal loudspeaker atstep S17. When the set 10 is mounted on a vehicle, i.e., used as amobile set, the speaker circuit 12 generates a mobile-mode ringing tonewhose frequency is suitable to the external loudspeaker at step S18.Steps S17 and S18 are followed by step S19 at which the control circuit9 monitors if it receives an off-hook signal indicating that the usergoes off-hook to start a telephone conversation. If the off-hook signalis not received within a predetermined period of time, the telephone set10 returns to the waiting state (step S11).

If the off-hook signal is received at step S19, the control circuit 9performs at step S20 a connection process in which the handset 14 isconnected to the receiver and transmitter portions 3, 4 in the portablemode while the microphone circuit 13 and the speaker circuit 12 areconnected to the transmitter and receiver portions 4 and 3,respectively, in the mobile mode. The completion of the connectionprocess allows the user to start a telephone conversation at step S21.

In FIG. 3, the speaker circuit 12 included in the speaker/microphoneportion 5 comprises a first ringing tone generator 31 for generating afirst ringing tone whose frequency is suitable to an internalloudspeaker 32 connected thereto. The speaker circuit 12 also comprisesa second ringing tone generator 33 for generating a second ringing tonewhose frequency is suitable to an external loudspeaker 35. Between thesecond ringing tone generator 33 and the external loudspeaker 35 isconnected a signal combining circuit 34 for combining the second ringingtone and a voice signal from the receiver 3 (FIG. 1). The externalloudspeaker 35 is to be connected to the signal combining circuit 34through a terminal 36 attached on a telephone set housing 37. While avoice signal is outputted through the external speaker 35 together withthe ringing tone in the mobile mode, a voice signal is outputted throughthe handset 14 (FIG. 1) in the portable mode. In the portable mode, onlythe ringing tone is outputted from the internal loudspeaker 32.

As mentioned above, the frequency spectrum of the first ringing signalproduced by the first ringing tone generator 31 is set so that itsubstantially corresponds to a relatively narrow frequencycharacteristics of the internal loudspeaker 32. On the other hand, thefrequency spectrum of the second ringing signal generated by the secondringing tone generator 33 is set so that it substantially corresponds toa relatively wide frequency characteristics of the external loudspeaker35.

A connector 38 mounted on the housing 37 is connected to the modedetecting circuit 8. The connector 38 is grounded when the telephoneset, i.e., the housing 37 is mounted on a vehicle. Thus, when theconnector 38 is not grounded, the mode detecting circuit 8 detects thatthe telephone set is in the portable mode while when the connector 38 isgrounded, the mode detecting circuit 8 indicates that the telephone setis in the mobile mode. The connector 38 may be constructed such that,when the external loudspeaker 35 is connected through the connector 36to the signal combining circuit 34, it is grounded simultaneously. Themode detecting circuit 8 provides a portable mode signal indicative ofthe portable mode to the first ringing tone generator 31 and a mobilemode signal indicative of the mobile mode to the second ringing signalgenerator 33. The call detecting circuit 7 detects a calling signal froma data signal from the receiving portion 3 and provides a call detectionsignal indicative of the presence of calling signal reception to boththe ringing tone generators 31 and 33.

With the FIG. 3 construction, when the telephone set is in the portablemode and there is a calling signal reception, the first ringing tonegenerator 31 is operated to send the first ringing signal to theinternal loudspeaker 32. In this case, since the frequency spectrum ofthe first ringing signal corresponds to the frequency characteristics ofthe internal loudspeaker 32, the first ringing tone generator 31 canoperate the internal loudspeaker 32 effectively with minimum power andthus the ringing can be performed effectively. On the other hand, whenthe telephone set is in the mobile mode and there is a calling signalreception, the second ringing tone generator 33 operates to produce thesecond ringing signal to the external loudspeaker 35. In this case,since the frequency spectrum of the second ringing signal corresponds tothe frequency characteristics of the external loudspeaker 35, the secondringing tone generator 33 actuates the external loudspeaker 35 with fullpower, so that it is possible to call with maximum volume of theexternal loudspeaker 35.

Referring to FIG. 4, an example of frequency characteristics of theinternal loudspeaker 32 is shown by a curve A and that of the externalloudspeaker 35 is shown by a curve B. These data were obtained based onthe output voltages of a microphone circuit which picks up sound fromthe respective loudspeakers under the same measuring conditions. Ingeneral, the internal loudspeaker 32 is compact and thus its soundgenerating efficiency is better in a narrow frequency band. On the otherhand, the external loudspeaker 35 does not provide high sound generatingefficiency although it exhibits a good frequency characteristics. Thecurve A indicates that the internal loudspeaker has a sharp peak at 2.9kHz with its output level being about 5.2 dBV. The curve A also showsthat the internal loudspeaker outputs an output level of about -1.5 dBVat 1.5 kHz and of about -3.5 dBV at 1.3 kHz. On the other hand, thecurve B exhibits that the external loudspeaker has a relatively widefrequency characteristics and its maximum output point is at 1.3 kHzwith level being about 0 dBV. Also, the external loudspeaker outputs anoutput level of about -7.0 dBV at 1.5 kHz and of -4.0 dBV at 2.9 kHz.

Setting the ringing signal frequency to a single frequency such as 1.5kHz which is the frequency of ringer of a cable telephone, there is noproblem for the external loudspeaker 35 since its frequency at which ahigh output level is produced is substantially coincident with theringer frequency. However, for the internal loudspeaker 32, its outputlevel at the ringer frequency is lower than the maximum output level byabout 7 dB. When such internal and external loudspeakers 32 and 35 aredriven by a ringing tone having such a single frequency, it isimpossible to operate the loudspeaker and the ringing tone generatorefficiently in either the portable mode or the mobile mode. However,when, as shown in FIG. 4, the frequencies of the first and secondringing tones respectively generated by the ringing tone generators 31and 33 are set at around 2.9 kHz and around 1.3 kHz, respectively, it ispossible to use the loudspeakers 32 and 35 and the ringing tonegenerators 31 and 33 efficiently. Moreover, each of the first and secondringing tones need not have wide frequency spectra and thus they can usea tone having a single frequency spectrum.

In FIG. 5, each of the ringing tone generators 31 and 33 comprises anoscillator 51 for producing a ringing tone, an oscillator power source52 for supplying power from a power source to the oscillator 51 and foron-off operating the power source and an AND gate 53 for on-offcontrolling the oscillator power source 52. To one input of AND gate 53a calling signal detection signal is supplied from the calling signaldetection circuit 7 and to the other input thereof a portable mode ormobile mode signal is supplied from the mode detecting circuit 8. WhenAND gate 53 receives these inputs, the gate 53 makes the oscillatorpower source 52 turn on so that the oscillator 51 produces the first orsecond ringing tone. More specifically, in the first ringing tonegenerator 31, AND gate 53 makes the power source 52 turn on when thegate 53 receives the calling signal detection signal and the portablemode signal. In the second ringing tone generator 33, AND gate 53 makesthe power source 52 turn on when the gate 53 receives the calling signaldetection signal and the mobile mode signal.

In FIG. 6, the mode detecting circuit 8 comprises a terminal 61 to whicha positive voltage is applied. To the terminal 61 is connected the oneend of a pull-up resister 62 the other end of which is connected to theconnector 38. To the connector 38 are connected the inputs of inverters63 and 64. The output of inverter 63 is connected to the input of aninverter 65 whose output is connected to the first ringing tonegenerator 31. The output of inverter 64 is connected to the secondringing tone generator 33.

In operation, when the connector 38 is grounded, i.e., the telephone setis mounted on a vehicle, the output of inverter 64 becomes a high levelindicative of the mobile mode, while the output of inverter 65 becomes alow level. Thus, only the second ringing tone generator 33 is enabled togenerate the second ringing tone. In contrast, when the connector 38 isnot grounded, i.e., the telephone set is removed from a vehicle, theoutput of the inverter 65 becomes a high level indicative of theportable mode, while the output of inverter 64 becomes a low level.Thus, only the first ringing tone generator 31 is enabled to generatethe first ringing tone.

FIG. 7 shows another example of the speaker circuit, denoted byreference numeral 12A, comprising a ringing tone generator 71 whichproduces the first or second ringing tone according to the use mode ofthe telephone set. The output of tone generator 71 is supplied to asignal combining circuit 72 to be combined with a voice signal from thereceiving portion 3. The output of combining circuit 72 is coupled to aspeaker switching circuit 73 which connects the output of signalcombining circuit 72 to one of the internal and external loudspeakers 32and 35. The external loudspeaker 35 is to be connected to the speakerswitching circuit 73 through the connector 36.

Although the use mode signal outputted by the mode detecting circuit 8may include the portable mode signal and the mobile mode signal asdescribed with reference to FIG. 6, here, an output level variation ofeither of the mode signals is utilized. The ringing tone generator 71produces the first ringing tone when the use mode signal is the portablemode signal and the calling signal detection signal is supplied. Thegenerator 71 also generates the second ringing tone when the use modesignal is the mobile mode signal and the calling signal detection signalis supplied. The signal combining circuit 72 combines the voice signaland the second ringing tone when the use mode signal is the mobile modesignal while it merely passes therethrough the first ringing tone whenthe use mode signal is the portable mode signal. The output terminal ofthe speaker switching circuit 73 is switched to the internal loudspeaker32 when the use mode is the portable mode and to the externalloudspeaker 35 when it is the mobile mode. Therefore, the ringing tonegenerator 71 of the speaker circuit 12 produces two kinds of ringingtones.

In FIG. 8, the ringing tone generator 71 is connected through a bus 81to the control circuit 9, which may comprise a microprocessor, thecalling signal detection circuit 7 and the mode detecting circuit 8. Theringing tone generator 71 comprises a clock generator 82 for generatinga clock signal. The clock signal is supplied to a frequency divider 83at which the clock signal is frequency divided. The divided clock signalis counted by a counter 84 whose output is applied to a read-only memory(ROM) 85. ROM 85 preliminarily stores patterns corresponding to thefirst and second ringing tone frequencies and provides one of the storedpatterns according to the output of counter 84. The output pattern ofROM 85 is supplied to a D/A converter 86 which converts the suppliedpatterns into a sinusoidal wave signal containing high harmonics. Alow-pass filter (LPF) 87 eliminates the high harmonics contained in theoutput of D/A converter 86 to provide a basic sinusoidal wave signal andan amplifier 88 amplifies the basic sinusoidal wave signal.

The frequency divider 83 divides the frequency of the clock signal by afirst frequency-dividing ratio when the portable mode signal is suppliedfrom the mode detecting circuit 8 and the calling signal detectionsignal is supplied from the signal receive detecting circuit 7. On theother hand, when the mobile mode signal and the calling signal detectionsignal are supplied, the frequency divider 83 divides the clock signalby a second frequency-dividing ratio. The counter 84 is used as adecoder for assigning addresses for ROM 85 and the output of counter 84when counted with the first frequency-dividing ratio reads the patterncorresponding to the first ringing tone frequency stored in ROM 85. Onthe other hand, the output of counter 84 when counted with the secondfrequency-dividing ratio reads the pattern corresponding to the secondringing tone frequency stored in ROM 85. In this manner, the two kindsof ringing tones can be digitally produced.

As described hereinbefore, the ringing circuit of the portable telephoneset according to the present invention includes the ringing tonegenerators for generating the first and second ringing tones whosefrequencies are set to be suitable to frequency characteristics of theinternal loudspeaker to be used in the portable mode and of the externalloudspeaker to be used in the mobile mode, respectively. The ringingtone is selected according to the use mode of the telephone set in whichthe associated loudspeaker is actuated. Therefore, it is possible toutilize the ringing tone effectively in either mode and to providemaximum ringing with minimum power consumption.

What is claimed is:
 1. A telephone set comprising:means for detecting a calling signal for said telephone set to produce a calling detection signal; means for detecting whether said telephone set is in a portable mode or mobile mode and producing first and second mode signals when said telephone set is in said portable mode and said mobile mode, respectively; generator means for generating a first ringing signal having a first frequency characteristic in response to said calling detection signal and to said first mode signal and generating a second ringing signal having a second frequency characteristic different from said first frequency characteristic in response to said calling detection signal and to said second mode signal; and switch means for providing said first ringing signal to an internal loudspeaker having a frequency characteristic corresponding to said first frequency characteristic in response to said first mode signal and providing said second ringing signal to an external loudspeaker having a frequency characteristic corresponding to said second frequency characteristic in response to said second mode signal.
 2. A telephone set as claimed in claim 1, further comprising means connected between said generator means and said switch means for combining said second ringing signal and a voice signal in response to said second mode signal and passing therethrough said first ringing signal in response to said first mode signal.
 3. A telephone set as claimed in claim 1, wherein said generator means comprises:a clock generator for generating a clock signal; a frequency divider for frequency dividing said clock signal based on said first and second mode signal to produce first and second divided signals, respectively; means for storing first and second patterns respectively corresponding to the frequency characteristics of said first and second loudspeakers, and producing the stored first and second patterns in response to said first and second mode signals, respectively; and means for converting the produced first and second patterns into first and second converted signals, respectively, and providing said first and second converted signals to said switch means as said first and second ringing signals, respectively. 